The present invention relates in general to a heavy duty lamp flasher for trucks and trailers and the like, and more particularly to an "in line" type flasher for turn signals for trucks and trailers.
Heretofore, a number of electronically controlled electro-mechanical relay type flashers have been previously used for causing flashing of the turn signals of trucks, trailers and the like, but problems have been encountered with these devices because of contact arcing reducing their useful service life and their load carrying capacity. Also, bimetal type and electromagnetically powered flywheel type flashers have been used for such applications, but these have encountered the same problems with contact arcing, resulting in reduced useful service life and load carrying capacity. Purely electronic type flashers have also been provided in an effort to overcome these problems, but such purely electronic types are expensive and fail to meet legal voltage drop requirements at high currents.
An object of the present invention, therefore is the provision of novel heavy duty lamp flasher circuitry for turn signals and flasher lamp applications for trucks, trailers and like vehicles, which relieves the problems encountered with prior art electromechanical relay type flashers and similar non purely-electronic flasher systems, to improve the service life of the flasher circuitry in such applications under conditions of heavy lamp loads.
Another object of the present invention is the provision of a novel heavy duty lamp flasher system for trucks, trailers and the like as described in the immediately preceding paragraph, which includes an active arc suppression circuit comprising a transistor in parallel with the switching relay to relieve problems of contact arcing and load carrying limitations of previously used electromechanical relay and similar type flasher systems.
Another object of the present invention is the provision of a heavy duty lamp flasher system and circuitry as described in the two immediately preceding paragraphs, wherein the relay in parallel with the transistor controls the transistor in such a way as to reduce contact arcing and enhance load carrying ability by causing the load to be shared by the switching devices and thus enable the device to switch currents in excess of the maximum ratings for either the transistor and the relay.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.